Humankind - Smart By Accident?

Science & medicine

When it comes to the human ego, scientists have been party poopers since Copernicus and Galileo told us that Earth is not the center of the universe.

Charles Darwin dumped more cold water on our divine spark with his theory of evolution.

It still seemed we had our heads for self-congratulation. Whoever our ancestors, the human brain is four times the size of any ape's and has five times the neurons of chimps' and gorillas'. It grew explosively in the last few million years - a blink by evolutionary standards - and has allowed us to bulldoze our way to planetary dominance.

Now anthropologists and psychologists are proposing our smarts are probably an accident caused by environmental pressures. Worse, we didn't evolve properly to think our way out of civilization's dilemmas.

In fact, psychologist Robert Ornstein, author of a new book called The Evolution of Consciousness (Prentice Hall, $25), dubs our brain the S.O.B., for Same Old Brain, and its component parts as ''simpletons.'' To get the point across, his book has cartoon illustrations showing dunce-capped brain cells.

''Our leap is largely an accident,'' the author said in a recent visit to Seattle.

The Los Altos, Calif., president of the Institute for the Study of Human Knowledge has written for a large lay audience. Ornstein's 1972 book, The Psychology of Consciousness, has sold more than 1.75 million copies.

The notion of a brain of mental simpletons clamoring with each other to build a mental picture of reality has been picked up by other writers as well, including a number of scientists at the Massachusetts Institute of Technology and philosopher Daniel Dennett of Tufts University, author of Consciousness Explained.

Ornstein calls for ''conscious evolution'' to overcome our limitations by better using the brains we have. As an example, he suggests educators spend less time on math skills that emphasize logic and more on probability because that is how our brains really make judgments.

''When was the last time you used algebra?'' he asked. ''Instead, people should be taught statistical theory and probability.''

University of Washington neurobiologist William Calvin, author of the earlier Ascent of Mind, is not much more consoling. ''It is impressive what humanity has done with what it had, bootstrapping itself up, but evolution doesn't always shape things for efficiency,'' he said.

Both address one of the mysteries of science: Why are we as smart as we are when related apes stayed and survived with far smaller brains? Why do humans seem so unique among species in intelligence and self-awareness?

Newer scientific theories based on recent archaeology flip-flop the timing, proposing that environmental stress led to larger brains with an excess of brain cells. In turn, those cells were tapped to make sophisticated tools, speech and self-consciousness possible.

Ornstein cites complicated recent proposals that much of brain growth stems from climate change in Africa, where humans evolved. As forests converted to grasslands, our ancestors came down from the trees, stood upright to see over the grass and pursued game by running it down.

Brains create heat, limiting their size to something that can be efficiently cooled. Ornstein's book suggests an upright posture produced immediate cooling, ''just as no one goes to sunbathe and stands.''

At the same time, the strain of chasing game across the widening savannahs created new heat stresses, which led to evolution of an improved circulatory system to cool the head. The brain also may have expanded to provide extra cells as a cushion against any lost to heat exhaustion. All this allowed the brain to swell, and our abilities with it.

''It isn't such a satisfying creation myth,'' Ornstein admits. ''Our intelligence may have been just an accidental benefit of heat packaging.''

Calvin said he ''likes that argument'' and has suggested something similar also occurred in the later ice ages. The challenges and opportunities produced by advancing and retreating ice sheets prompted brain growth as a survival mechanism, he proposes, and the more advanced humans at the edge of the ice subsequently dominated the planet.

Calvin notes, however, that none of these theories is entirely satisfactory.

Why didn't brain enlargement occur in a few other species with the same environmental pressures, he asked. The best answer to date is that human ancestors brought a peculiar bundle of abilities to a peculiar set of circumstances. This in turn raises the question of whether the evolution of intelligence is inevitable or a fluke, commonplace in the universe or rare.